Police sealed off the A350 after receiving reports of a suspected bomb in Portal Road, Melksham, where building work is taking place at the old running track behind the Christie Miller Sports Centre.

A bomb disposal unit arrived just before 3.30pm to examine the device, which is thought to be about three feet long and date from the First World War.

Roads were closed around Bowerhill and the main A350 near the Semington roundabout but have now been reopened.

PCSO Matt MacLaughlan said it was believed that what had been found was much bigger than the old RAF shell which was found on Thursday, October 2, and a wide cordon had been put in place as a precaution.

A worker at the site of the new Herman Miller factory found the suspected bomb and alerted site manager Josh Butler, who called the police.

It was X-rayed by a bomb disposal unit and police said the 200lb shell did not contain any explosives.

On October 2, digger driver Alan McConnell, who made the previous discovery, said: “I was digging holes and as I pulled a load of muck up, it was in the bucket.

"I thought it was a piece of cast iron, so I shook it about to get the muck off and realised 'ooh it’s got a rounded head on it, that’s a bomb'.”

David Merrills, Collins Earthworks project manager, called to the police to report the previous finding.

He said then: “We are all aware that we are working on what used to be an RAF base and there could be possible bombs."